The heterodimeric integrin family of receptors modulate cellular shape and cell adhesion to the extracellular matrix in response to extrinsic and intrinsic cues.
Integrin signaling controls cell survival, cell cycle progression, cell differentiation, and cell migration.
The integrin receptor exclusively can signal a cell bi-directionally, both “inside-out” and “outside-in.” Thus, they mediate cell migration by transmitting forces from the extracellular matrix to the cytoskeleton and regulate cytoskeletal organization to achieve shape changes needed during cell migration.
Integrins are expressed on the surface of most of human cells. Their pathology contributes to a diverse set of human diseases, including platelet disorders, atherosclerosis, cancer, osteoporosis, fibrosis, diabetic neuropathy of the kidney, macular degeneration and various autoimmune and chronic inflammation diseases.
Integrins form heterodimers of two different chains: the at (alpha) and R (beta) subunits. The α4β7 integrin is expressed on lymphocytes and is responsible for T-cell homing into gut-associated lymphoid tissues through its binding to mucosal addressin cell adhesion molecule (MAdCAM), which is present on high endothelial venules of mucosal lymphoid organs.
Inhibitors of specific integrin-ligand interactions have been shown effective as antiinflammatory agents for the treatment of various autoimmune diseases. For example, monoclonal antibodies displaying high binding affinity for α4β7 have displayed therapeutic benefits for gastrointestinal auto-inflammatory/autoimmune diseases, such as Crohn's disease, and ulcerative colitis.
The role of integrins as drug targets has long been recognized, and a total of six injectable integrin inhibitors have been approved by the Food and Drug Administration for the treatment of various therapeutic indications: inflammatory bowel disease (Entyvio®, Tysabri®), multiple sclerosis (Tysabri®), psoriasis (Raptiva®), and acute coronary syndrome (Reopro®, Aggrastat®, Integrilin®). However, there has been a notable absence of therapeutic success with orally bioavailable integrin inhibitors.
Of the twenty-four known integrin heterodimers, as least half have relevance in inflammation, fibrosis, oncology and vascular disease. Thus, there exists a need for new classes of integrin inhibitors.